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Relating population signals to synchronized spiking activity

Hypothesis: Assembly activations are tightly coupled to oscillations of the local field potential

Link the population dynamics to precisely coordinated spike timing within neuronal assemblies

Denker et al. 2011, figure 1

An inspiring yet hotly debated hypothesis states that cortical networks employ the coordinated activity of groups of neurons, termed assemblies, as a means to code information. Despite recent advances in increasing the number of recorded neurons in electrophysiological experiments and in developing novel analysis tools to handle such complex data, the massive undersampling of the system still prevents us to directly observe assembly activity in the living brain. Still, a growing body of experimental studies indirectly substantiates the assembly idea with findings of behavior-related significant synchronous spiking activity. Independently thereof, a mesoscopic signal probing the neural population, like the local field potential (LFP), typically exhibits temporally structured oscillations commonly interpreted as correlated network activity. Likewise, the occurrence and strength of such oscillations are linked to behavior. In this project, we aim to establish direct links between coincident spiking events on the millisecond time scale and LFP oscillations based on data taken from the motor system of the awake behaving monkey. Indeed, first results reveal that assembly activity detected by a pair-wise Unitary Event analysis exhibits an exceptionally strong phase locking to the LFP cycle that cannot be explained by the phase-locking of individual neurons alone. In the future, we aim to extend our approaches to spike correlations of higher-order, and to explain the connection between the two scales of observation using modeling approaches.